This invention relates to a device for connecting one end of a liquid medicament delivery cannula to an apparatus for connecting a syringe to a vial containing the medicament.
Medicaments exist which are preserved under sterile conditions in vials sealed by a rubber, silicone or similar stopper. The medicament is withdrawn from the vial by a syringe provided with a needle which punctures the rubber stopper, to penetrate into the vial. Often, the syringe is used to inject into the vial a liquid (solvent, physiological solution or the like) in which the medicament is dissolved or diluted inside the vial. The liquid together with the pharmaceutical substance dissolved in it is then drawn into the syringe for subsequent use.
Often, in order to avoid contaminating the needle and, in special cases, the environment (when very dangerous medicaments such as antitumoral medicaments are present) and thus to protect persons handling the syringe and vial from danger, special arrangements of various types must be used, the most simple of which is to fit on to the free end of the syringe an apparatus which surrounds and protects the needle. This apparatus comprises a seat into which the mouth of the vial can be inserted so that it remains secured to the apparatus. The syringe is then moved towards the vial so that the needle point punctures the rubber stopper of the vial. In this manner, the possible solvent can be fed into the vial and the medicament solution be drawn into the syringe under very safe conditions, because the needle, the vial stopper and any medicament droplets lie within a closed environment bounded by the said apparatus and, at its two ends, by the syringe and vial.
Apparatus of this type are described in U.S. Pat. Nos. 3,336,924, 3,826,260 and 3,995,630, in European published patent application No. 126,718 and in Italian published patent application No. 19785 A/84, corresponding to Belgian pat. No. 901,699. European patent application No. 126,718 and Italian patent application no. 19785 A/84 provide a sealing member (in correspondence with that seat of the apparatus which is to house the vial mouth), above which the point of the syringe needle is made to rise before the vial is removed from said apparatus. In this manner, even after the medicament has been drawn into the syringe, no contamination of the needle or of the external environment can take place because the needle is entirely housed within a closed chamber bounded by the apparatus, by the syringe and by said sealing member.
When the medicament is to be used, either the apparatus is removed from the syringe to thus leave the needle free (with all the dangerous contamination consequences which should have been avoided), or a device has to be inserted into the said apparatus seat to allow this apparatus to be directly connected to a discharge cannula for the medicament. The cannula can for example carry at its free end a needle (such as an epicranial needle) for transfusing the medicament into the vein directly from the syringe.
The possibility (whish is in effect a necessity) of using such a type of device fitted to one end of the cannula and fixable into said apparatus seat was described for the first time in Italian patent application no. 19785 A/84 and subsequently in European patent application No. 126,718.
In Italian patent application No. 19785 A/84, it states that the device mounted on the end of the cannula "has a profile completely analogous to that of the vial". It has been found in practice that it is impossible (especially for cost and space reasons) to give this device exactly the shape of the vial. However, if the device reproduces only the shape of the vial mouth (ie of that part provided with the rubber stopper and the relative ring which fixes it to the vial), the device very easily and very frequently penetrates with its axis inclined to the axis of the apparatus seat, with the result that the connection device can jam in the apparatus seat or penetrate only partially into it, so leaving an empty space between the rubber or similar stopper provided on the device and the sealing member provided in the apparatus in correspondence with the containing seat into which the device has been inserted. Medicament droplets can penetrate into and collect in this empty space when the syringe needle is lowered to pass through the sealing member of the apparatus and then through the rubber stopper of the device, with obviously dangerous consequences.
The device for connecting the medicament discharge cannula to the apparatus which protects the syringe needle as illustrated in European patent application No. 126,718 is of very complicated construction (and therefore practically unimplementable), as can be easily seen by examining FIG. 4 of this patent, in which the device is shown in section.